Stabilization of cellulosic fabrics by applying alkyl silicon halide vapors



A 2,782,090 Patented Feb. 19, 1957 United States Patent Ofifice STABILIZATION OF CELLULOSIC FABRICS BY APPLYING ALKYL SILICON HALIDE VAPORS Edward Robbart, Cambridge, Mass.

No Drawing. Application July 21, 1954, Serial No. 444,917

13 Claims. (Cl. 8-11 6) t This invention consists in a process of treating cellulosic fabrics with organo halogenosilanes to improve their stability against shrinkage.

.A major problem in finishing fabrics of cellulosic fibers, such as cotton, acetate or rayon fabrics, is in minimizing shrinkage during subsequent washing of the fabric or of articles made from the fabric. In applicantscopending application, Serial No. 318,734, filed November 4, 1952, is disclosed process of treating fabrics with .organo 'halogeno sila es which, among other things, improves That process consists in gentheir shrinkage resistance. eral of exposing the fabric to vapors of the silane under carefully controlled conditions of time and temperature, and then neutralizing the reaction by-products in a mildly alkaline solution and drying the fabric.

The present invention constitutes an improvement ove the invention of ,applicants prior application whereby better shrinkage stabilization isattained, either with or without imparting water repellency to the fabric. In addition, the process of this inventionavoids the difficulties previously encountered in treating cellulosic, fabrics with organo halogeno silanes of degradation caused by acidic reaction by-products, r

The process of this invention consists in general of. ex-

posing the fabric togaseous mixture, preferably an aerosol, of an organo halogeno silane and an inert gas .at a temperature no higher than about 100 F., and preferably below 80 F., for a brief period of time generally between one second and five minutes, then immediately thereafter From the foregoing brief description, it will be seen that applicants 'presen'tlinvention differs from the process of his copending application primarily in that the fabric is tensionedduring'drying. Why tensioning should result I in better stabilization against shrinkage is not fully understood, but it has been found that whereas the prior process is etfective to reduce shrinkage of a cotton muslin to less thanabout 3%, by the process of the present invention, shrinkage maybe reduced to less than 1%. From this it will be seen that the process of this invention compares favorably with the well-known compressive shrinkage process (sanforizing) Where it is. desired that the treated fabric shall be waterrepellent in addition to being stabilized, the fabric should, prior to exposure to the silane vapors, have a moisture content such as attained by equilibrating the fabric with an atmosphere of about 30-90% relative humidity. Howevenit may be desired that the fabric be temperature of 200 F. or higher.

Silanes preferred for practicing the invention are the 'n'iethyl chloro silanes, such as methyl trichloro silane, Ql-IsSiClg, dimethyl dichloro silaneKCHahSiClz, methyl tlichlorosilane, CHs-SiHClz, and commerciallyavail'able methyl chloro silane compositions consisting principally of methyl trichloro silane, climethyl dichloro silane and trimethyl chloro silane (CHs)3SiCl (together with some methyl dichloro silane, and silicon tetrachloride SiClr, as these result from the method of manufacture), as they are readily available and sufficiently volatile to be formed into vapors at low temperatures. Mixtures of trimethyl chloro silane and silicon tetrachloride are also satisfactory. It is contemplated, however, that other organo halogeno silanes may be used particularly the lower alkyl silicon halides (e. g. ethyl, propyl, butyl, etc., silicon halides). In forming the gaseous mixture for treating the fabric, the silane may be allowed to evaporate. in air, or other inert gas, but is preferably atomized to produce an aerosol mixture, in the form of a noticeable fog. In this manner, the silane concentration of the gas mixture may be greatly increased over that attainable by true vaporization within the temperature limitations. An aerosol formed by condensation, as by cooling a saturated atmosphere of silane, may also be employed.

The fabric is exposed to the silane atmosphere for be tween about one second and five minutes, preferably for less than a minute, and is then immediately immersed in a mildly basic aqueous neutralizing bath, preferably one buffered at a pH of between 7 and 11. Alkaline neutralizing agents particularly suitable for forming the bathinclude sodium carbonate, sodium bicarbonate, calcium hydroxide, disodium phosphate, trisodium phosphate, sodium acetate, and similar water-soluble basic compounds which form slightly basic aqueous solutions of high neutralizing capacity. Strongly basic solutions, e. g. of pH higher than 11.0,, are preferably avoided since they tend to remove the silicone from the fabric. Dilute solutions of such strongly basic materials as sodium hydroxide having a pH below 11 could be used, but the neutralizing capacity is quite low because of the extreme dilution of the solution necessary to such low alkalinity. Ammonia and amines are also preferably avoided as neutralizing agent's. since their salts, formed during neutralization, tend to be retained by the fabric and cause gradual degradation. The neutralizing bath preferably also includes a wetting agent effective to aid the wetting ofv cellulosic fabrics, preferably a nonionic or cationic wetting agent, examples of which are well-known in the art.

After neutralization, the fabric is. preferably rinsed in water to remove residual alkaline solution and is then tensioned and dried. ,The tensioning of the fabric is preferably widthwise, that is, in the direction of the fill threads, with little or' no tensioning warpwise, to permit normal contractionof the warp threads during drying; Tensioning and drying is preferably carried out in a standard commercial tenter-dryer, preferably one adapted to be overfed to permit warpwise contraction during drying. In so tensioning the fabric it is preferably drawn out at least to substantially its original dimension preceding exposure to the silane vapors, and is typically stretched by between about one and five percent.

When drying is complete the tension is released, and after a few minutes during which the fabric relaxes and contracts, the fabric will be stable and undergo generally not more than 1% shrinkage during subsequent washings.

Warpwise tensioning, particularly when accompanied by widthwise tensioning, is also satisfactory but generally results in greater initial relaxation and contraction when the tension is released,

The following examples describe in detail representative and preferred embodiments of this invention, and are presented as illustrative thereof.

Example 1 An enclosed chamber was supplied with an atmosphere of: an aerosol mixture of methyl chloro silanes consisting chiefly of methyl trichloro silane and dimethyl dichloro silane (GE Drifilm, sold by the General Electric Company, Schenectady, New York), by atomizing the silane in the container until it was filled with a noticeable fog, at a temperature of about 75 F. An unfinished cotton muslin piece measure 60" x 60" and equilibrated at room temperature at a relative humidity of about 60% was then placed in the chamber for about seconds, and then removed and immediately immersed in a warm (ca. 100 F.) concentrated aqueous solution of sodium bicarbonate, containing a small amount (e. g. about 0.02% by weight) of a wetting agent such as the nonionic wetting agent Triton X 100 sold by Rohm & Haas Co., Philadelphia, Pennsylvania, and described as an alkyl aryl polyether alcohol), and was agitated therein for about 1 minute. After rinsing the muslin in cold water, it was stretched on a pin frame to a width (fillwise) of 63", the other edges remaining free, and was permitted to dry. When the fabric was removed the width returned to 60 inches. did not shrink more than 1% in either direction. This fabric showed a pronounced Water-repellency in that water showered on it formed droplets which were readily shed.

Example 2 The same procedure described in Example 1 was followed with the exception that prior to exposure to the silane vapors the fabric was dried in an oven at 220 F. The treated fabric showed substantially the same stability as that treated in accordance with Examplc 1, but was not water-repellent. Water showered on this sample was readily absorbed, wetting the fabric.

Example 3 In a continuous process a plain weave rayon 60 inches wide, having a warp count of 90 threads/ inch and a filling count of threads/inch, and weighing 16 oz. per linear yard, was passed through a chamber having an aerosol atmosphere as described in Example 1. The fabric was passed through the chamber at rate providing a dwell therein of about 20 seconds, and fresh silane was atomized in the chamber at a rate of 2 parts by weight for each 100 parts of fabric.

After passing through the chamber, the fabric was passed through a neutralizing bath, of composition the same as given in Example I, and then through rinse water to remove excess alkali.

The fabric was then finally dried in a standard tenterdrier adjusted to grasp the selvedge edges and expand the fabric to a width of about 61 inches, and to overfeed the fabric by about 10%. When dried the fabric was released from the tenter, upon which the width returned to inches, and was found not to shrink during ten subsequent washings by more than about 1.5%.

By way of comparison, a similar fabric, treated in the same way but dried without being tentered, shrunk by about 3-4% after three washings. It will accordingly be seen that tensioning of the fabric during the final drying and after treatment with the silane results in a marked improvement in the stability of cellulosic fabrics.

The foregoing examples have been presented as illustrative of applicants invention and it is contemplated that obvious modifications will occur to those skilled in the art and may be made without departing from the scope of this invention.

In addition to the fabric disclosed in the examples, the process of this invention may be used advantageously with other cellulosic fabrics and includesin general, the treatment of fabrics of such fibers as cotton, rayon, and cellulose acetate.

The chemical mechanism by which the process func tions is not fully understood but it is theorized that a reaction takes place on and within the fibers between the silane and hydroxyl groups in the cellulose molecule During ten subsequent washings, the fabric (see in this connection Schuyten, Weaver, Reid and Jergens, J. Am. Chem. Soc. 70, 1919 (1948)) and between adsorbed moisture on the fibers and the silane. The latter reaction is believed to account for the water repellency characteristics of the treated fabric, for presumably by it is formed a surface coating of a silicone. As evidenced by the fact that a dried fabric may be treated as described in Example 2, to impart shrink resistance without substantial water repellency, it appears that the theorized reaction with cellulose hydroxyl groups somehow accounts largely for the improved shrink resistance resulting from the treatment, probably by altering the ability of the fibers to absorb water and relax during subsequent washings.

The foregoing explanation is presented as hypothesis and is not intended as limiting in any way this invention to the theorized mechanism.

Having thus disclosed my invention and described in detail preferred embodiments thereof, I claim and desire to secure by Letters Patent:

1. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups, comprising exposing the said fabric for not more than about 5 minutes and at a temperature of less than about 100 F. to organo silicon halide vapors, having as organo substituents alkyl groups with between one and four carbon atoms, the conditions of time and temperature being such that reaction takes place between the halogen of said organo silicon halide and said free hydroxy groups with the liberation of free hydrogen halide, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric at least to substantially its original dimension preceding exposure to said vapors and drying it while held under tension at said dimension, whereby said fabric is stabilized against shrinkage.

2. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups, comprising exposing said fabric for not more than about 5 minutes and at a temperature of less than about 100 F. to vapors comprising a material selected from the group consisting of: methyl trichlorosilane; dimethyl dichlorosilane; methyl dicholorsilane; trimethylchlorosilane in admixture with silicon tetrachloride; and mixtures of the foregoing materials, the conditions of time and temperature being such that reaction takes place between the chloride of said material and said hydroxy groups with the liberation of hydrogen chloride, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric at least to substantially its original dimension preceding exposure to said vapors and drying it while held under tension at said dimension, whereby said fabric is stabilized against shrinkage.

3. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups comprising exposing said fabric at a temperature of about F. to no higher than about F. and for a time between about I second and 5 minutes to organo silicon salide vapors having as organo substituents alkyl groups with between one and four carbon atoms, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric at least to substantially its original dimension preceding exposure to said vapors and drying it while held under tension at said dimension, whereby said fabric is stabilized against shrinkage.

4. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups comprising exposing said fabric at a temperature of about 75 F. to no higher than about 100 F. and for a time between about 1 second and 5 minutes to vapors comprising a material selected from the group consisting of: methyl trichlorosilane; dimethyl dichlorosliane; methyl dichlorosilane; trimethylchlorosilane in admixture with silicon tetrachloride; and mixtures of the foregoing materials, immediately thereafter neutralizing and-removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric at least to substantially its original dimension preceding exposure to said vapors and drying it while held under tension at said dimension, whereby said fabric is stabilized against shrinkage.

5. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups, comprising exposing the said fabric for not more than about minutes and at a temperature of less than about 100 F. to organo silicon halide vapors having as organosubstituents alkyl groups with between one and four carbon atoms, the conditions of time and temperature being such that reaction takes place between the halogen of said organo silicon halide and said free hydroxy groups with the liberation of free hydrogen halide, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric fillwise at least to substantially its original width preceding exposure to said vapors anddrying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

6. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups, comprising exposing said fabric for not more than about 5 minutes and at a temperature of less than about 100 F. to vapors comprising a material selected from the group consisting of: methyl trichlorosilane; dimethyl dichlorosilane; methyl dichlorosilane; trimethylchlorosilane in admixture with silicon tetrachloride; and mixtures of the foregoing materials, the conditions of time and temperature being such that reaction takes place between the chloride of said material and said hydroxy groups with the liberation of hydrogen chloride, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric fillwise at least to substantially its original width preceding exposure to said vapors and drying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

7. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups comprising exposing said fabric at a temperature of about 75 F. to no higher than about 100 F. and for a time between about 1 second and 5 minutes to organo silicon halide vapors having as organo substituents alkyl groups with between one and four carbon atoms, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric fillwise at least to substantially its original width preceding exposure to said vapors and drying it while held under tensecond and 5 minutes to vapors comprising a material width preceding exposure to said vapors and drying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

9. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups comprising exposing said fabric at a temperature of about 75 F. to no higher than about F. and for a time, between about 1 second and 5 minutes to organo silicon halide vapors having as organo substituents alkyl groups with between one and four carbon atoms, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric fillwise to stretch it by at least about 1% and drying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

10. The method of stabilizing water insoluble cellulosic fabrics having free hydroxy groups comprising exposing said fabric at a temperature of about 75 F. to no higher than about 100 F. and for a time between about 1 second and 5 minutes to vapors comprising a material selected from the group consisting of: methyl trichlorosilane; dimethyl dichlorosilane; methyl dichlorosilane; trimethylchlorosilane in admixture with silicon tetrachloride; and mixtures of the foregoing materials, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric fillwise to stretch it by at least about 1% and drying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

11. The method of stabilizing fabrics including a material selected from the group consisting of cotton fibers and cellulosic rayon fibers having free hydroxy groups comprising exposing said fabric at a temperature of about 75 F. to no higher than about 100 F. and for a time between about 1 second and 5 minutes to organo silicon halide vapors having as organo substituents alkyl groups with between one and four carbon atoms, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric fillwise at least to substantially its original width preceding exposure to said vapors and drying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

12. The method of stabilizing fabrics including a material selected from the group consisting of cotton fibers and cellulosic rayon fibers having free hydroxy groups comprising exposing said fabric at a temperature of about 75 F. to no higher than about 100 F. and for a time between about 1 second and 5 minutes to vapors comprising a material selected from the group consisting of: methyl trichlorosilane; dimethyl dichlorosilane; methyl dichlorosilane; trimethylchlorosilane in admixture with silicon tetrachloride; and mixtures of the foregoing materials, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH between 7 and 11, then tensioning the fabric fill-wise at least to substantially its original width preceding exposure to said vapors and drying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

13. The method of stabilizing fabrics including a material selected from the group consisting of cotton fibers and cellulosic rayon fibers having free hydroxy groups comprising exposing said fabric at a temperature of about 75 F. to no higher than about 100 F. and for a time between about 1 second and 5 minutes to vapors comprising a material selected from the group consisting of: methyl trichlorosilane; dimethyl dichlorosilane; methyl dichlorosilane; trimethylchlorosilane in admixture with silicon tetrachloride; and mixtures of the foregoing materials, immediately thereafter neutralizing and removing the resulting by-products by immersing the fabric in a basic aqueous solution having a pH'between 7 and 11, then tensioning the fabric fillwise to stretch it by at least about 1% and drying it while held under tension at said width, whereby said fabric is stabilized against shrinkage.

References Cited in the file of this patent UNITED STATES PATENTS Patnode Dec. 22, 1942 Norton Dec. 10, 1946 Pfett'er et a1. Feb. 17, 1948 Thayer June 28, 1949 

1. THE METHOD OF STABILIZING WATER INSOLUBLE CELLULOSIC FABRICS HAVING A TREE HYDROXY GROUPS, COMPRISING EXPOSING THE SAID FABRIC FOR NOT MORE THAN ABOUT 5 MINUTES AND AT A TEMPERATURE OF LESS THAN ABOUT 100*F. TO ORGANO SILICON HALIDE VAPORS, HAVING AS ORGANO SUBSTITUTES ALKYL GROUPS WITH BETWEEN ONE AND FOUR CARBON ATOMS, THE CONDITIONS OF TIME AND TEMPERATURE BEING SUCH THAT REACTION TAKES PLACE BETWEEN THE HALOGEN OF SAID ORGANO SILICON HALIDE AND SAID FREE HYDROXY GROUPS WITH THE LIBERATION OF FREE HYDROGEN HALIDE, IMMEDIATELY THEREAFTER NEUTRALIZING AND REMOVING THE RESULTING BY-PRODUCTS BY IMMERSING THE FABRIC IN A BASIC AQUEOUS SOLUTION HAVING A PH BETWEEN 7 AND 11, THEN TENSIONING THE FABRIC AT LEAST TO SUBSTANTIALLY ITS ORIGINAL DIMENSION PRECEDING EXPOSURE TO SAID VAPORS AND DRYING IT WHILE HELD UNDER TENSION AT SAID DIMENSION, WHEREBY SAID FABRIC IS STABILIZED AGAINST SHRINKAGE. 